Modify date printing to fetch time zone name before converting to local time,...

Modify date printing to fetch time zone name before converting to local time, so that the two agree.  Fix a problem in DateToTimeString() time zone calculation.

Committed: http://code.google.com/p/v8/source/detail?r=4342

[William Hesse, 2010-03-31 13:12:24]

This change uses the fact that fetching the time zone string checks and updates
the cached local time offset.

It also corrects an existing problem where Date.toTimeString()  fetches the time
zone name
based on the local time, not based on the UTC time.
Time zone code is all designed to take UTC arguments.
Only that one function is wrong.  toString and toDate are
correct.

The failure is shown below:
> w = new Date(w)
Sun Mar 28 2010 01:30:00 GMT+0100 (CET)
> w.toString()
Sun Mar 28 2010 01:30:00 GMT+0100 (CET)
> w.toTimeString()
01:30:00 GMT+0200 (CEST)

[Erik Corry, 2010-04-06 08:59:37]

LGTM